When you are painting, it is a good idea to know about how much paint you will need to finish the job. You will want to box (marry or mix) all the same color paint. This will ensure color consistency for touch up purposes. You also don’t want to finish your painting project with a color that is slightly off. This can cost you your time and money. If you are going to be applying two coats then, make sure you have the same amount for the second coat. It is also a good idea to have extra for touch up. If you are purchasing paint that is not pre-tinted (stock) or medium to deep tones, I always recommend boxing the paint. When I am painting inside, I will always box my paint because inconsistencies in the paint color and sheen are easily detected. In my line of work we have a saying,” material is cheap, and labor is expensive!” Take the time and box your paint!